A conventional sealing device for providing a seal between a crawler bushing and a crawler link of such a crawler belt is constructed of a seal contact end face of the crawler bushing and a seal member which is inserted in the crawler link to abut on the seal contact end face. This sealing device has its service life often determined by wear of the seal contact end face of the crawler bushing, rather than wear of the seal member. Thus, a measure against the wear of the seal contact end face of the crawler bushing needs to be taken to improve the seal service life.
An example of the crawler bushing having the seal contact end face with wear resistance is disclosed in patent document 1.
As shown in FIG. 10(a), plate 102 which underwent wear-resistant coating is attached to the seal contact end face of crawler bushing 101 of patent document 1with adhesive 103. In crawler link device 100 equipped with this crawler bushing 101, seal member 105 inserted in crawler link 104 makes contact with wear-resistant plate 102, whereby the wear of the seal contact end face of crawler bushing 101 is suppressed.
However, this crawler link device 100 problematically faces time-consuming replacement of wear-resistant plate 102 which is attached to crawler bushing 101 with adhesive 103.
Accordingly, crawler bushing 111 disclosed, for example, in patent document 2is conceivably adopted.
As shown in FIG. 10(b), crawler bushing 111 of patent document 2is provided with annular recess 112 in its end face, and corrosion-resistant annular insert member 114 having corrosion resistance is inserted into this recess 112 via elastic ring 113. In crawler link device 110 equipped with this crawler bushing 111, seal member 116 inserted in crawler link 115 makes contact with corrosion-resistant annular insert member 114, whereby the wear of the seal contact end face of crawler bushing 111 is suppressed. It is to be noted that when inserted into recess 112, corrosion-resistant annular insert member 114 deforms elastic ring 113 by giving ring 113 a slight squeeze. For this reason, corrosion-resistant annular insert member 114 experiences resilience from elastic ring 113 in response to the squeeze and is thus urged in a sealing direction, that is, in the direction of arrow P pointing outward along an axis of crawler bushing 111.
According to this crawler link device 110, corrosion-resistant annular insert member 114 is simply squeezed into recess 112 of crawler bushing 111 via elastic ring 113, so that insert member 114 can be replaced with ease.
However, the resilience of elastic ring 113 that is exerted on corrosion-resistant annular insert member 114 is strong in this crawler link device 110. Accordingly, insert member 114 presses seal member 116 with excessive force. This causes damage and early wear to seal member 116 which as a result has an impaired sealing function. Consequently, oil leakage may problematically occur.